For interference to disappear, it is necessary that human experimentalists know which path the photon takes. True or false?

True. In the context of experiments like the double-slit experiment, interference patterns occur when it is unclear which path a photon takes—meaning that the experiment lacks "which-path" information. If experimentalists gain knowledge of the path taken by the photon, this "which-path" information destroys the superposition of paths and results in the disappearance of the interference pattern. This phenomenon is closely related to the principles of quantum mechanics, where observation affects the behavior of quantum particles.